Draft Beer Systems 101

Draft beer systems may seem somewhat complicated at first glance. But once you tackle the basics, you’ll see that they’re actually quite easy to understand. From keg pressure settings and standard definitions, to keg dimensions and pouring techniques, we’re here to tell it all. Quench your thirst for knowledge and become a smarter, more educated draft beer connoisseur.

Glossary of Draft Beer Terms

Draft Beer

Any type of beer that is drawn from a large vessel. Kegs aren’t the only “vessels;” the term “draft beer” includes cask ale as well.

Keg

Metal container used for storing and dispensing pressurized liquids. A single hole centered at the top of the keg and a two-way valve allows liquids to be added and removed from the keg.

Keg Beer

Unpasteurized beer that is dispensed from a keg using gas pressure.

Direct Draw Draft System (Standard Draft System)

Technical name for specialized equipment built specifically for dispensing keg beer from a temperature-controlled environment through the use of compressed gas. Direct draw draft beer systems may be housed in a kegerator, walk-in cooler, or converted refrigerator.

Keg Volume and Dimensions

Note: These measurements apply to standard US kegs. US keg dimensions may vary slightly by manufacturer and brewery. European kegs vary in size, but are similar to US sizes.

½ KegHolds 15.5 gallons – approximately 165 12-ounce bottles
Weighs 161 pounds when full
24″ high with a 16″ diameter

¼ KegHolds 7.75 gallons – approximately 82 12-ounce bottles
Weighs 87 pounds when full
12-13″ high with a 16″ diameter

1/6 KegHolds 5 gallons – approximately 54 12-ounce bottles
Weighs 55 pounds when full
24″ high with an 11″ diameter

The Basics of Keg Pressure

Pressure is an imperative component of all fully-functional draft beer systems. It’s what keeps your beer carbonated and tasting fresh all the way from keg to glass. Having too much or too little pressure will affect the way your beer is dispensed, and you won’t be able to enjoy its full potential. These keg pressure pointers will help you find that perfect medium.

About Head Space

As CO2 enters a keg, it displaces your beer at a constant pressure. When you open the tap/faucet, beer flows out of the keg and into your glass due to a push from the CO2. The gas then fills the space where the beer was formerly housed, and that’s the “head space.” The CO2 fills the head space and maintains the pressure inside of the keg at the PSI set on your CO2 regulator. This constant PSI keeps the beer carbonated by preventing CO2 leakage.

Keep it Straight

Your CO2 tank must be stored upright or it won’t work properly. Storing the tank improperly can also cause expensive damage to your regulator.

Find the Magic Number

Most ales and lagers produced in the US should be dispensed at 10 – 12 PSI. Stout and other nitrogen-reliant keg beers are usually dispensed at 25 – 30 PSI.

For the specific dispensing pressure for a particular keg, check with your local distributor.

Too Much Pressure

Too much pressure will leave you with foamy beer that comes quickly out of the faucet. If your beer is over-carbonated, the foam will appear tight with large bubbles.

If you encounter this problem, it’s easy to fix. Adjust your regulator pressure to the proper lower level and draw a few foamy pitchers. You can also use your coupler’s relief valve to bleed out the extra pressure. These measures will force your system to balance itself out again.

If the pressure is left too high for too long, CO2 will be forced into the beer resulting in permanently over-carbonated and excessively foamy beer. Thus, it’s important that you address this problem as soon as the issue is identified.

Too Little Pressure

Too little pressure will also force foam because the CO2 can break free from the beer as it enters your glass. If the pressure is not raised to the appropriate level, your beer will eventually become flat.

When you see foam or bubbles visibly rising in your beer hose, this is a telltale sign of low pressure. If your beer is under-carbonated, the foam will look loose, often described as appearing “soapy” with small bubbles.

To correct this problem, you should first make sure that your CO2 tank is properly turned on with gas remaining inside. Then, check to see the level at which your beer regulator is set. If your tank is functioning properly, you’ll know that your regulator is set to the right number and there are no obstructions in the air line. If this is the case, you may need to replace your regulator or gauge. Regulators do wear down with time and use, so you should generally replace them every 4-6 years.

Keg Tips, Tricks, and Rules to Remember

Keep it Calm

After any sort of transport or travel, give your keg some time to settle down. If you don’t, you’re likely to experience excessive foaming at tapping time. Remember that the beer inside of a keg is carbonated, so moving or shaking it will cause it to foam – just like a can of beer or soda. We recommend that you let your keg sit for an hour or so after transport.

Keep it Cold

Keg beer is unpasteurized, so it has to stay cold to stay good. As a general rule, think of keg beer as you think of milk: it needs to be refrigerated at all times. Keep your kegs between 34 – 40 degrees Fahrenheit and your beer will remain fresh and delicious.

Keep it Fresh

The beer inside a keg will retain its full flavor about 30 – 45 days after tapping. It’s difficult to pinpoint an exact amount of time, as a keg’s “shelf-life” is dependent on storage conditions and the brand/style of the beer. Generally, hoppy beers and those with a higher alcohol content will last longer because the hops and alcohol act as preservatives, inhibiting the growth of bacteria.

Keep it Clean

When beer does go bad quickly, it’s almost always one (or both) of two culprits: oxygen and/or bacteria. Unfortunately, bacteria will eventually spoil unpasteurized keg beer – even when the keg is kept in the perfect storage conditions.

Modern scientists have discovered that the only way to beat the bacteria is to drink all of the beer in your keg, before the bacteria has a chance to ruin it – usually in that 30 – 45 day range. Should you require critical consumption assistance, KegWorks research has found that good friends are usually willing to help.

The other culprit, oxygen, is particularly harmful to kegs tapped with a hand pump. A hand pump forces air (containing oxygen) into the keg, which in turn, forces the beer out. This is good. However, as soon as the oxygen is introduced in the keg, it causes the chemical reaction called oxidation.

Oxidation will cause the beer inside of a keg to go flat and acquire a sort of sour taste. Thus, a keg tapped with a hand pump should be consumed within 24 hours. Thankfully, neither of these processes render beer harmful to humans, but they do make it undrinkable.

56 Comments

SteveMay 11, 2015 @ 5:22pm

when i first tap a keg (always a craft brew IPA) it tastes great as intended for about 5 days or so. After that, its still okay, but not great like it was in week 1. After the second week, another drop off in taste. Still drinkable, but a far cry from two weeks ago. Am i doing something wrong with my CO2 pressure or is this just the nature of the beast? I use 5 gallon kegs in a refridgerator conversion kegerator. temp 37F, pressure 10-12psi. No foaming issues, great pours every time. (seven foot beer lines took care of the foaming). At 10-11 psi i get bubbles developing above the coupler (suggesting low pressure?) if i raise the pressure just to the point that those bubbles dont form (12-13psi), the beer loses flavor almost instantly (over carbonation?) What am i doing wrong?

Modern IPAs are in some ways the most delicate beers in the world, as a huge chunk of their flavor is from delicate aromatics, which can cook off. Just for the sake for experimentation, dump (or set aside) two pints before you pour a pint to smell and taste. If that third pint tastes right, then you know the problem: all the beer you were drinking was that which was sitting (and aging) in the line. For one person’s kegerator, you generally want to stick with the shortest, thinnest line possible. If your beer line is bigger than 3/16″ ID, there’s half your problem right there.

Hands down I think you are cranking too much pressure just to push an IPA. Depends on the brand of IPA you are buying & where it was intended to be. But I RARELY push beer out of my keg at more than 6psi. Here is why: If you have more pressure than the beer was originally carbonated at then you are adding co2 to your beer every day.. Most IPAs are good at 2-2.5 co2 volumes(I’d aim for 2 personally especially given your issue.) Here is a chart to show you where you should be. http://www.kegerators.com/carbonation-table.php looking at this table it says 37degrees and 12psi = 2.62 volumes if your thermostat or regulator is even a little off you are ADDING co2 to your beer, thinning it out and making it spritey. I think you should aim much lower like 6psi.

IPAs are meant to be drunk fresh. They are often dryhopped and kettle hopped, and these flavours and aromas can deteriorate rapidly with age. That is likely why you are experiencing this problem with IPAs.

Every time I buy a new keg and hook it up I get all foam, the term true is in the low forties, my pressure gage is on about 10psi, still get foam , I i adjust the pressure up or even lower than 10psi , nothing seems to help,, I’m hoping you will have a solution.

Thanks for reaching out. First of all, I’d suggest lowering the temperature even more. 40 should be the highest, but you generally want to be in the 34-40 degree (Farenheit) range. Secondly, what kind of beer are you pouring? Ales and Lagers are good at 10-12 PSI, but Stouts and other nitrogen-reliant beers are best at 25-30.

Lastly, are you seeing loose foam or small bubbles visibly rising in your beer lines? If so, the pressure is probably too low. Since you’re dispensing at 10 PSI, I can’t imagine it’s too high.

Let me know about the kind of beer you’re pouring, take a look at possibly upping the PSI, depending on the beer, and try to hit that 34-40 degree sweet spot with your temperature. If that doesn’t work, we’ll re-assess. You can also always give us a call with questions at 877-636-3673.

just a quick question, my c02 is at 8psi and temp is 38 serving yuengling and sam but its foamy with little tiny bubbles… i had it at 12psi and it was foaming like crazy so i turned the co2 to 8psi and no help really. almost the whole glass is foam…system was just cleaned and was working fine for the past year, now nothing seems to help

Hi, Vikki. We need some additional information to assess this properly. How long are the lines running from the keg to the faucet? Is it the first glass you pour every time? There could be a few things at play, so it may be best to call customer care at 877-636-3673.

I work for Miller/Coors. I would ha e to guess the beer at the faucet has raised temperature well over 40° two things the line and faucet need to be below 35° (visible condensation on the faucet), and be sure to open the faucet all the way you may even need to give the faucet a good cleaning or replace it.

I have a converted Guinness system that has worked great for 1 1/2 years. It was last tapped approximately a month ago. Worked great for two weeks. I then went on vacation for two weeks and it went untouched. Upon returning, it poured a half a glass and then went straight to foam. Every glass thereafter has been all foam. PSI remains at 28. Lines look fine. Nothing had changed. As I was at a total loss as to what was wrong, I replaced with a standard faucet just to see how it poured. It poured very fast since it was not a Guinness faucet but flowed black and immediately turned to foam in the glass. Could someone shed some light on what may be wrong? We are approaching football season and I desperately want Guinness flowing again.

That stinks, and we definitely understand the desire for fresh Guinness during football games. Why don’t you give us a call at 877.636.3673, and we can talk this through with you. Just describe the issue you’re having, and one of our Customer Care members will gladly walk you through some troubleshooting advice.

The 28 is too high, for too long. 28 psi in a busy place is ok, becasue there is no time for the beer to get over carbonated. Short draw 10 – 12psi , long draw 15 – 22psi that ‘s it. What you can do is shake your keg and then prime the pressure inside your keg until you get ridden of the over carbonation just make sure you don t do it too much you may get flat beer. Works like a soda can. Also the Guinness foam is created by the faucet so you don t need 28. Good luck

Actually your pressure is fine for this one (maybe even a tad low). Your problem sounds like it is your gas blend. Guiness is a special beer called a nitro stout, it has a very low content of CO2 in it (typically 1.1 volumes by volume (similar to wine) whereas craft beers are 2.5 and domestics usually are 2.7). You want to push guiness with a 25% CO2 gas blend and a 75% nitrogen blend at a high pressure with a restrictor faucet. At this high pressure you can actually get a little bit of nitrogen absorption into your guiness. The end product is a good flow rate at your tap with the restrictor setup and a cascading effect as the nitrogen rises out of the beer quickly and pushes the co2 down. If you are using 100% co2 you are putting way way too much co2 under a high pressure into your guiness keg and you are going to overcarbonate your guiness and foam like a son of a gun. Change your gas blend and voila, problem solved. Nitrogen is actually used in other long draw set ups (higher pressure) to counteract the foaming in normal ales and lagers as well. Typically these setups will only require 40% nitrogen to counteract the CO2 absorption as you don’t need to displace as much CO2 because of the higher levels of CO2 that are already present in the beer. Now all of this can change depending on your temperatures….remember chemistry 101 where they told you that the soluability of gases rises in liquids as temperature decreases??? Temperatures, pressures, gas blends, and volume by volume, welcome to beer science.

I am kegging my home-brew for the first time. I keep my co2 regulator at 12 psi and lower it a little bit when I’m ready to dispense. While dispensing (I am using a picnic tap at the moment), I notice the co2 level going down. If my regulator is on, should it automatically take the keg pressure back to 10-12 psi? This has not been the case. I am manually turning the knob on my taprite regulator to put it back to these levels. Is there a way to maintain the levels w/o turning the knob every few drafts or is this normal and OK?

don’t lower it when you are ready to dispense, as the head space increases in your keg you want that CO2 going back into your headspace to keep your beers carbonated and from the CO2 breaking out of solution. Why were you lowering your CO2 pressure when you went to dispense in the first place? Was it coming out too fast? You want a flow rate of 2 ounces per 1 second so the co2 won’t break out of solution by slamming into the glass, time it yourself (7 seconds for a 16 ounce pint as the last two ounces should be a nice head at the top of the glass, doesn’t have to be dead on but you want to be somewhat close). If its coming out too fast you can always add a little restriction by lengthening your line, but don’t adjust your pressure down when dispensing it will only hurt your beer, and really doesn’t serve a purpose cheers!

I gave your email to one of our Draft Beer Account Executives, and he’s going to be in touch with you. In the meantime, you can also feel free to shoot us an email at beer@kegworks.com, or give our Draft Beer guys a call at 866.881.BEER (2337).

I have a 3 tap system kegerator. Co2 tank is inside the kegerator. It pours fine with 3 sixtels but when I have a 1/2 keg and 2 1/6’s after about 80-90 pours from the 1/2 keg all 3 taps pour at a dribble adjusting psi (regardless of up or down)allows the 1/6’s to pour but the 1/2 pours all foam. This only seems to happen when I have 1/2 keg combined with 2 1/6’s. No one can correct! Is it due to the uneven kegs and psi requirements? Please advise thank you

What is your pressure at? how long is the 1/2 barrel lasting compared to the 1/6 barrels? What kind of beers are you pushing in each, craft, domestics, etc? Are you using one regulator, or are you using a step down regulator at each keg (think one reg per keg)? Let me know…

There is almost certainly a leak somewhere. Make sure all of your connections are tight. You could try unhooking your keg and cranking up your regulator to 30 PSI to help you hear if there is a hiss of CO2 escaping somewhere in your lines/couplers. Good luck.

2 of the 5 taps are working properly but the middle 3 i am having an issue with. One beer doesn’t come out at all, one is very low and the other just isn’t as consistent as the two working ones. can Anyone help with my dilemma?

I am new to having a kegerator. I am on my 4th keg of bud light. Before I installed this last keg cleaned my lines. Used cleaner for kegs. I installed new keg and 2 days later no beer would dispense. I shut off my co2 and found tank empty. The next day I replaced the next day. Fast forward a week later the beer taste slightly bitter and has a slight sweetness to it. I again cleaned the lines suspecting dirty lines no luck. My temperature has been about 34 degrees running 8-10 psi. Please Help! Keg has a lot of beer left. Beer was purchased 12-23. I was getting a lot of foam also.

My wife bought me a single tap kegerator for christmas. I just added a dual tap. Everything was good the first day. the next day my tap handle was stuck. After using a lot of force I was able to pull the handle but no beer comes out. The other Tap works fine, pours beer. I noticed my co2 pressure is down to 3-4 psi. I think my co2 bottle is close to being empty but on the other hand it still pours beer out of my other tap. What could be the problem? The co2 bottle has just a little over 2 kegs on it. Any answers would be appreciated

I have a older taprite co2 regulator that I have rebuilt with new diaphragm and gauges. When hooked up to a new bottle of co2 that is over 500 psi it will push gas out the weep hole in the diaphragm cover. When pressure is at 500 psi it stops leaking and last as normal, any ideas?

I have a 3 tap system 2 could and 1 nitro. Poured a few pint of Guiness today andau just went for a third and nothing is coming out. Nitro tank is good, keg still has beer. Tap is opening, what could it be?

Hi, Michelle. There are a few things it could be. Is your gas at the appropriate pressure? For mixed gas, it should be 30 psi. Are your lines free of kinks and twists? You also want to make sure the coupler is engaged and the check ball is not lodged anywhere. Also, check that the faucet and shank are clean and that the lower part of faucet is clear of obstruction. I hope this helps!

Ok, my husband and I have a kegorator, that we bought from SAMs. We have had it for about five years. Every keg that we have ever bought for it was bud light. This time, when the last leg ran out. I cleaned the lines and unplugged the keg. We were going out of town. When we returned, we decided to get a keg of Stella. We brought it home, tapped it and nothing will come out. There is no beer in the line at all. The CO2 tank is on and there is pressure. We are at a loss. Any suggestions.

I’ve had a problem with commercial 1/6th barrel kegs being too foamy. My kegerator is an old fridge I modified with eight Perlick taps installed through the door. I primarily use corny kegs but occasionally grab a commercial 1/6th barrel of something or other. I use proper 3/16th” beer serving line. My Co2 distribution uses back flow preventers and the regulator is set at 11.5 PSI. Everything is kept religiously clean with true TSP and sanitized with iodophor.

I initially had issues with the corny kegs dispensing foamy beer but learned how to calculate serving line length and that solved my problem. With commercial 1/6th barrel kegs they always start out very foamy but over time (weeks/months) this evens out. I always allow the keg to settle for 24+ hours before tapping it. Once the foam in a glass subsides the beer appears and tastes properly carbonated.

The foam has a mix of tiny (sub mm) bubbles and bubbles about 3-4mm in size. It’s not thick or rocky nor thin like milk. When I open the tap there is an initial rush of foam which fills about 3/4 of a pint glass and then beer comes out.

This instance involves a keg of Dogfish Head Festina Peche. When I first tapped it I immediately pulled the pressure relief valve on the tap and very little pressure came out and I could hear Co2 cycling through the back flow prevention valve so this indicates the beer is under carbonated but I’m not certain.

This really irritates me especially at $109 for a 1/6th barrel! Is commercially kegged beer fully carbonated when filled? Any ideas on how to fix this problem?

Hi there. We need some additional information to assess the problem properly. Where is the kegerator located? When did you start using it? It sounds like you are getting temperature differential foaming, which happens when the cold beer hits the warm metal shank and faucet.

Thanks for the reply. The kegerator is inside my house. No issues with sunlight or heater vents. I built the kegerator about 8 years ago. The shanks of my taps are 100% inside the door. I even made and installed blue board foam insulation around each shank where it penetrates the door.

I currently have 4 corny kegs in there and have no problem at all with them. The issue only affects the one commercial 1/6th barrel keg. The serving line on that keg is almost touching the ceiling of the kegerator and has about a 3.5″ drop from the highest point to the shank.

I’m running 6 taps on a long draw with beer gas. Kegs totally flat at bottom. From what i’m reading we need to go back to Co2. Is it ok to switch to Co2 on the partial kegs that have been running beer gas?

Hi, Mike. There are a few factors that go along with gas choice, restrictions of your system being the biggest. If you use a high pressure of CO2, it will over carbonate the beer. We recommend sticking with beer gas since it is long draw, but you may need to change the blend.

Question: We have a direct draw two tap system that is a fridge directly under the taps. There is probably at most 14 inches of line from the inside of the fridge up (at the base of the counter) up into the tap. Each night, they untap the keg and run the line to ensure it is shut off. For some reason, the bartender seems to think that the tap needs to run until the ‘bubbles’ are gone and then places the glass under the flow. In my experience (and it’s been a while), there is no need to run the line like that and if there are bubbles in the line during each pour, something is wrong with the line. I haven’t noticed it when I pour, but I also brew beer with my husband and know a little more about craft beers then my bartender seems to have now. My question is, should there be “bubbles” in the line between pours? If there are truly bubbles, what is causing it? I think my bartenders are wasting allot of beer because of this and since the line is so short, there should be no reason to waste all that first pour. Does re-tapping every day cause problems? (If so, why would they build a system to do that?) Thank you!!

Hey guys I am headed out to purchase my first Keg for my new kegorator, the fridge came with a cO2 tank and regulator. my question is this: If i wanted to purchase a stout of any kind do I need to also buy a nitro tank? Do all stouts use nitro? Where is the cutoff line as far as types of beers that use nitro and types that use cO2, or can most beers use cO2? Any info helps, Thanks

Definitely not all stouts are Nitro beers you should definitely say whether it’s a Nitro or not unless it’s Guinness and they’re like well you should know but in my opinion most Stouts do taste better with Nitro.

Question: Recently looked at a beer problem for a customer, the two dark beers are pouring heavy(foamy), all other beers are fine. Glycol tank at temp, keg room at 7 degrees but CO2 pressure seemed a little high at 38-38 psi. Reduced CO2 pressure to 30psi but customer tells me same two beers are still pouring heavy after 24hrs. Both kegs were also depressurised, any ideas ?

I’m working on a N2 issue at one of our accounts. The beer they are pouring is a local N2 Porter that puts out 1.4 vol similar to Guinness. The PSI regulator is set at 30. The cooler temp fluctuates between 34-38. They have a 75/25 N2/CO2 mix but it’s a Green Air Supply separator box that naturally separates the N2 and that trickles into a primary reservoir tank and that’s the source they use. It’s been pouring great for years but recently they’ve had some issues with their cooler getting too cold and dropping below freezing. (30-34 degrees) We’ve notice that this is dramatically affecting the N2 pours making them seem sort of flat and not cascading properly. Would the dramatic temperature drop somehow cause the Co2 level in the keg to decrease and flatten the beer over time? If so how should we adjust the PSI to compensate? If not, what would cause the beer to start to pour flat over time with those settings the way they are? (We’ve done a gas leak check and ran a diagnostic check on the Green Air box and all the tests came back positive for working right) Any help on this is much appreciated. Thanks